Color photographic elements typically contain several records each with silver halide sensitized to a different region of the visible light spectrum. Generally, one record is sensitized to red light, another green light and another, blue light. Each of the foregoing records also contains a color coupler which reacts with oxidized developer during processing of the element, to produce a dye in a pattern corresponding to the image to which the element was exposed. In a typical element the red, green and blue sensitive records respectively contain a cyan dye forming coupler, a magenta dye forming coupler and a yellow dye forming coupler.
As to the colour couplers, these are known to belong to a number of classes, for example magenta dye-forming couplers can be pyrazolones, pyrazolotriazoles and pyrazolobenzimidazoles while yellow dye-forming couplers can be acetanilides. European Patent Specification 0 431 374 A describes .beta.,.gamma.-unsaturated nitriles as cyan colour couplers of the general formula: EQU R.sub.2 --V.dbd.C(R.sub.1)--CH(W)--CN
wherein
W is hydrogen or an atom or group capable of being released when the compound is subjected to a coupling reaction with oxidised product of an aromatic primary amine derivative and is attached to a carbon atom having an sp.sup.3 electronic configuration, PA1 R.sub.1 is a substituent, PA1 V is nitrogen or --C(R.sub.3).dbd., PA1 if V represents nitrogen, R.sub.2 represents a substituent, PA1 if V represents --C(R.sub.3).dbd., R.sub.2 and R.sub.3 each represent a substituent, provided that at least one of R.sub.2 and R.sub.3 represent an electron attractive substituent, and provided that if R.sub.2 or R.sub.3 represents an aliphatic group or an aromatic group, the other does not represent an acyl group, and PA1 R.sub.1 and R.sub.2 may bond together to form a ring.